The present invention relates to a cleaning method for removing deposits on a surface of a material to be treated, specifically to a cleaning method for removing deposits adhering firmly to a surface of a material to be treated without damaging the material to be treated.
When a surface of a material to be treated is cleaned with a cleaning agent, damage such as corrosion has been exerted on the surface of the material to be treated by too strong detergency in a certain case.
In these days, a lithography is one of indispensably important techniques as a production process for a highly integrated semiconductor device. When a semiconductor device is produced using lithography, formed on a substrate such as a silicon wafer are a conductive thin film of a metal film which is a conductive wiring material and an interlayer insulating thin film such as silicon oxide film having a purpose of providing insulation between wirings; then, a photoresist is applied evenly thereon to form a photosensitive layer; and this is subjected to selective exposure and developing treatment to form a desired resist pattern. Then, this photoresist pattern is used as a mask to subject a silicon oxide film on a lower part to selective etching treatment, whereby a desired pattern is formed on the above thin film. Then, the above photoresist pattern is completely removed to finish a series of steps.
In recent years, ultra high integration in a semiconductor device is advanced, and it has been required to form a pattern of quarter micron or less. As a dimension in such processing goes on toward ultra fineness, a dry etching method has come to be a main stream in selective etching treatment, and ashing carried out by oxygen plasma has come to be used for removing a resist pattern. This ashing means to remove a resist comprising, for example, an organic polymer in the form of CO and CO2 by combustion reaction by virtue of oxygen plasma generated in plasma. It is known that when carrying out dry etching treatment, produced in a peripheral part of a pattern formed are a dry etching gas, a resist and a processed film and a residue (hereinafter referred to as an etching residue) originating in a processing chamber member in a dry etching apparatus. If such etching residue remains particularly in an inside of a via hole and a peripheral part thereof, an increase in a resistance of a semiconductor device is brought about or electric short circuiting is caused, and therefore it is not preferred.
Further, in recent years, a Damascene process is used as a production process for a highly integrated semiconductor device when a simple substance of copper is used for a wiring material. The fundamental Damascene process which is applied at present shall be explained below. As shown in FIG. 4, (a) a silicon oxide film 2 for providing insulation between wirings is formed on a silicon wafer 1 by a CVD method; a photoresist 3 is applied evenly on the surface thereof to form a photosensitive layer; and this is subjected to selective exposure and developing treatment to form a desired resist pattern 4. (b) This photoresist pattern 4 is used as a mask to subject the silicon oxide film 2 in a lower part to dry etching treatment, whereby a desired pattern 4a is formed. In this case, an etching residue 8 remains on the pattern 4a. (c) The photoresist 3 and the etching residue 8 are completely removed. (d) In order to inhibit copper from diffusing, a TaN (tantalum nitride) layer 5 is evenly formed in an inside of the pattern 4a on the silicon oxide film 2 by a PVD method, and then a copper thin film layer 6 which is a conductive wiring material is formed thereon by the PVD method or plating treatment. (e) The surplus films of copper and TaN which are not required are removed by a CMP method, and the copper thin film layer 6 is polished together with the silicon oxide film 2 to achieve flattening, whereby an initial wiring layer A is formed. (f) A silicon nitride film 7 is formed by a plasma CVD method in order to inhibit copper from diffusing between a wiring layer which is formed on an upper layer later and the initial wiring layer A described above. Then, (g) a wiring layer A2 is further formed on the initial wiring layer A by repeating the steps of (a) to (f), whereby a desired wiring layer is formed.
Organic amine base peeling solutions comprising a mixture of alkanolamine and an organic solvent are disclosed as a cleaning solution for removing an etching residue, a cured resist layer and a resist in such a production process for a semiconductor device in, for example, Japanese Patent Application Laid-Open No. 49355/1987 and Japanese Patent Application Laid-Open No. 42653/1989. However, when washing with water is carried out after removing an etching residue, a resist and the like, amines contained in these cleaning solutions are dissociated by virtue of moisture absorbed to show alkalinity, so that a metal film is corroded, and therefore involved therein is the problem that an organic solvent such as alcohol is required as a rinsing solution.
Further, fluorine base aqueous solutions comprising a fluorine compound, an organic solvent and a corrosion inhibitor are disclosed as a cleaning solution having a higher capacity for removing an etching residue, a cured resist layer and a resist than that of an organic amine base peeling solution in Japanese Patent Application Laid-Open No. 201794/1995 and Japanese Patent Application Laid-Open No. 67632//1999.
In recent years, however, processing conditions in dry etching in a production process for a semiconductor device become severe, and a resist surface layer is more changed in property, whereby a cured resist layer is formed, and it has become impossible to completely remove them with the organic amine base peeling solutions and the fluorine base aqueous solutions described in the respective official gazettes described above. Further, an etching residue which is left standing without removing brings about electrical troubles such as an increase in a resistance, breaking of wire and short or unusual circuiting, and therefore strongly desired is a cleaning solution which can completely remove the etching residue, the cured resist layer and the resist for forming a mask which is unnecessary after dry etching each described above. Also, ashing by the use of oxygen plasma can be used as well for removing a resist pattern which becomes unnecessary. This ashing means to remove a resist comprising, for example, an organic polymer in the form of CO and CO2 by combustion reaction by virtue of oxygen plasma generated in plasma. However, in this ashing, that is, in a method for removing a photoresist by oxidation, copper is notably oxidized, and a low resistance which is a merit thereof is damaged. Accordingly, it is very important to remove a resist changed in property by etching without damaging a copper wiring material.
The present invention has been made in order to solve the problems described above, and an object thereof is to provide a cleaning method by which deposits adhering firmly to a surface of a material to be treated can readily be removed without damaging the material to be treated.
The present invention provides a cleaning method characterized by allowing a cleaning agent comprising an oxidizing agent, a chelating agent and a fluorine compound to flow on a surface of a material to be treated at a high speed to thereby clean the above surface to remove residues on the surface of the material to be treated on an inorganic substrate.